1. Field of the Invention
The present invention relates to a video printing apparatus which, with respect to an original video image having a framed dither image area in a specific area of one image, can print an image corresponding to an arbitrarily designated image area or areas on a printing sheet at a determined area.
2. Description of the Related Art
Various types of video printers are known which are responsive to various types of video signals, such as an NTSC reference composite video signal, RGB analog signal and RGB TTL signal, to print a corresponding image on a printing sheet. For example, the following two types are generally known:
(1) A small-image video printer having its scanning image number (for example, 480.times.480, 480.times.600) near the number of scanning pixels of a video signal and its printing image size of 80 mm.times.(80 to 100) mm.
(2) A video printer having its scanning pixel number about two times as many as the number of pixels of the case (1) in the horizontal and vertical directions and its printing image size about four times as large as that of the case (1).
The printer (1) as set out above is of such a type that one original video image is printed on a printing sheet. The printer (2) as set out above is of such a type that one original video image is printed on a printing sheet or four original video images are printed on a printing sheet without being reduced in size.
As one form of application, a video printer is used to prepare a printing image for dealing with a "diagnostic image" or "recording image for diagnosis" on a body cavity of a human subject which is imaged by an endoscope. The "diagnostic image" is employed in almost all cases for diagnosis only, but the "recording image" is employed often together with a clinical chart for a patient. A printing sheet is preferably of such a type that a printing image size is below 80 mm.times.100 mm and that, conveniently, a plurality of scenes are printed on a printing image sheet as required. In the latter case, respective original video images are printed on an image sheet on a reduced scale in which case, if printing is performed by a conventional small-image video printer, an image emerges in a poor image quality. Stated in another way, the printing image is such that the number of constituent pixels are so fixed as to be substantially equal to that of an original video image. When printing is done with the original video image reduced in size, an image emerges with the number of pixels of each printing image decimated or thinned out, resulting in a poor image quality with some image information dropped.